Ecologist + shed = home-made canopy sampler

Today, it's time to move away from obscure invertebrates and have a look at the kit I use to find some of these things - not the usual pooters, beating trays and nets, but something a little more unusual.

I do quite a lot of invertebrate-hunting in all sorts of habitats - grasslands, heathlands, woodlands, coastal areas and so on. Of these, one is particularly tricky - woodland. At ground level it's fine, but I can't help but wonder what's up in the canopy that I can't get at - certainly there's a lot of recent research into canopy ecology around the world (e.g. here) following realisation of its importance alongside some technical advances aiding the research work itself. On a large scale and/or with lots of funding, there are various options - smoking whole trees, building canopy walkways, laying flexible platforms across the treetops, and so on. On a smaller and cheaper scale, there is the option of hoisting flight interception traps into treetops and leaving them to see what falls in before returning to collect the catch. This is something I can do, but a lot of my surveys involve a limited number of visits quite widely separated. This means that traps would have to be left for too long and might suffer from interference from members of the public (unless tied off further up the trees, but that means climbing). So, I got to thinking about how to sample the canopy whilst actually on site and without having to get roped and harnessed.

This meant being able to get a sampling device in and out of the canopy at will, and that the device had to be sufficiently portable to carry by hand from the nearest access point (which can be some distance away). Although tempted by something involving a remote-control helicopter, this seemed fraught with dangers of both cost and getting it stuck up a tree. Nope, that idea was quickly scrapped in favour of something else - a lightweight telescopic pole with a canopy sampler on the end. So, how does that work..?

First, get a series of aluminium poles and cut/fit them as follows:

A set of aluminium poles, three of which have a short section of narrower pole riveted into one end so that they are interlocking. Drill holes through so that they can be fitted together and held in place with wing-nuts. The fourth one has a hook at the end to catch and shake branches and can also be bolted into place. If you think your drilling may vary a bit between poles, which would mean they have to fit in a particular order, number your first three poles 1-3...

Short section riveted into large section

Wing-nut fixing in situ

Hooked end on pole four. A wire hangs from the bend with one or more loops (to adjust the height of the sampler) at the end. This could equally be strong cord or any other suitable material.

That's the pole arrangement, but what about the sampler? This requires an inverted truncated cone open at both ends with a smooth inner surface (try an unwanted lampshade). This has a long thin bag (fine mesh; the one below was made from net curtain) sewn onto the smaller hole and strings for suspension (via a carabiner or similar clip) attached over the larger hole.

Sampler consisting of bag, cone, strings and carabiner modelled by our washing line...

This is clipped onto looped wire and the whole thing hoisted up into a tree canopy - the hook is then used to shake branches, dislodging invertebrates which then helpfully fall into the cone and slide into the mesh bag.

The sampler in action, modestly extended, and modelled lovingly by me in our back garden...

So, onto the main question - does it work? Well, I have tried it on a number of surveys and the answer is yes. The whole arrangement is 4+ metres long so with the user's height/reach means that it can sample up to about 6 metres above the ground. Although some specimens undoubtedly escape as with nets and beating trays, each use has provided species which had been missed by sampling directly below at ground level. I have yet to undertake a rigorous study but hope to find some time to quantify exactly which groups it is best for, although initial indications are that weevils are one group readily captured. I'm also hoping to find that some under-recorded canopy-dwelling groups and species are readily caught, but only time (and sampling/identification effort) will tell, so watch this space!